The proposed research is focused on the endocrine control of mammalian meiosis. The investigation of the control of entry into meiosis by fetal germ cells or re-entry by adult oocytes and the inhibition of fetal female meiosis during prophase and adult preovulatory prophase will be investigated. The specific experiments involve (1) application of the hormonal control of the in vitro female meiotic switch to the absence of meiosis in male fetuses, (2) analysis of localization of LH and its subunits in the primed oocyte with radioautography and immunologic techniques, (3) detection of tublin in fetal and adult oogenesis with H3 colchicine and radioautography and (4) evaluation of potential serum and follicular fluid inhibitors using the in vitro oocyte maturation test and general separation and purification techniques.